Atomic diffusion barriers and inter-element miscibility guide the development of unexplored crystal phases

Z3-Fe(Pd,In)₃ ordered alloy nanoparticles containing alternating layers of an L1₀ (CuAu-type)-like PdFePd trilayer and a Pd-In ordered alloy monolayer are formed by following the inter-element miscibility of In, which is miscible with Pd but immiscible with Fe. An understanding of the atomic diffusion processes based on inter-element miscibility is required to effectively synthesize such unknown crystal phases. In this study, we demonstrated that the temperature required for the formation of the Z3 structure largely depends on the diffusion path of Fe into PdIn _x or In into FePd₃ alloy nanoparticles. The results indicate that the design of the diffusion path should be considered to develop unexplored crystal phases, especially in alloy systems containing an immiscible pair of elements.